Kaolin-supported NiCo-LDH nanocontainers for self-healing and anti-corrosion epoxy coatings

Abstract

Considerable attention has been paid to the corrosion protection of metals due to economic and environmental issues. Among the available approaches, organic-inorganic coatings remain the most practical and economical barrier technology. Nevertheless, conventional formulations frequently suffer from limited durability, inadequate adhesion, and elevated production costs, which restrict their large-scale deployment in harsh environments. In this study, kaolin served as a substrate for the hydrothermal co-precipitation of NiCo-LDH, resulting in K/NiCoLDH composites. Gallic acid (GA), an organic corrosion inhibitor, was then intercalated into the NiCo-LDH structure to form K/NiCoLDH@GA nanocontainers, which were added to an epoxy matrix to enhance corrosion resistance and self-healing capabilities. Structural characterization demonstrated the effective combination of kaolin and NiCo-LDH, and confirmed GA intercalation into the LDH interlayers. Electrochemical measurements and laser confocal microscopy revealed that K/NiCoLDH@GA effectively inhibited the corrosion of Q235 steel by providing both barrier protection and active ion exchange.The prepared K/NiCoLDH@GA/EP coating was further evaluated through long-term electrochemical tests in a simulated seawater environment, showcasing sustained protective performance. To examine self-healing behavior, an artificial scratch was introduced on the coating surface, and the repair process was monitored via scanning Kelvin probe (SKP). Results indicated that the release of GA from the nanocontainers significantly reduced localized corrosion at the defect site. Overall, the K/NiCoLDH@GA nanocontainer system offers a promising, cost-conscious pathway for designing robust and eco-friendly corrosion-resistant epoxy coatings in demanding marine environments.